Nomenclature of Tire

Tires outer perimeter, often called the crown, has various designs of jagged shaped grooves in it, known as the tread. These grooves are especially useful during weather with rain (or snow). The water from the rain is compressed into the grooves by the vehicle's weight, providing better traction in the tire-to-road contact. The sidewalls are the sections of the tire which are between the crown & the inner circular edges of the tire contacting the rim. To avoid tearing at these inner edges, particularly when the tire is being mounted, there are a number of concentric steel wires buried inside the rubber at both inner edges of the tire. This inner rim is called the bead.

Air-filled tires, especially those used with spoked wheels such as on bicycles & motorcycles, or on vehicles travelling on rough roads, have an inner tube; this was also formerly the case of automobile tires. This is a fully sealed rubber tube with a valve to control flow of air in & out. Others, including modern radial tires, use a seal between the metal wheel & the tire to maintain the internal air pressure (tubeless tire). This method, however, tends to fail desperately if the vehicle is used on rough roads as a small bend on the rim (metal wheel) will result in deflation. The inner tubes are usually made of halobutyl rubber, because of its suitable mechanical properties & excellent impermeability for air.

Pneumatic tires generally have reinforcing threads in them; based on the orientation of the threads, they are classified as bias-ply/cross ply or radial. Tires with radial yarns (known as radial tires) are standard for almost all modern automobiles.